'High cholesterol genes' discovered

09:43Thursday 11 October 2012

Scientists are "a step closer to preventing heart attacks" the Daily Mail reports. The newspaper says that the largest ever genetic study of its kind paves the way for personalised drugs and treatments.

This large study has combined the results of 32 studies that have looked at the association between genetic make-up and blood lipid (fat) profile in more than 65,000 Europeans. The researchers were looking for what are known as single-nucleotide polymorphisms or SNPs. An SNP is a single “letter” DNA variation in the genetic code, and researchers use them as “markers” to identify areas of DNA that may contain genes associated with different traits and diseases.

The researchers were interested in whether there were specific SNPs that were associated with higher levels of cholesterol and other fats (lipids) in the blood, and identified several SNPs that had not been previously established to be associated with blood lipid profile.

Overall, this study furthers our understanding of which genetic variants may influence the fats we have in our blood. Even so, these genetic variations will not provide the whole answer. It is not yet clear whether this study brings us “a step closer to preventing heart attacks” or paves the way for new treatments.

We do not currently have the ability to alter our genes. What we can do to reduce our risk of cardiovascular diseases is to eat a healthy balanced diet high in fruit and vegetables, take regular exercise, stop smoking and drink alcohol in moderation. Read more about reducing your cholesterol levels.

This research was conducted by extensive international researchers and was published in the peer-reviewed scientific journal American Journal of Human Genetics. Sources of funding were not reported by the researchers.

This is a well conducted meta-analysis that has combined the results of 32 European genetic studies.

However, the implications of its findings are exaggerated in the media. Learning more about the genetics of certain conditions can lead to new treatments, as was the case with breast cancer. But this may not be the case with high cholesterol. Even if people with certain genetic variations do have a tendency to have higher cholesterol, the treatment they are given is unlikely to change. They may be given treatment to lower their cholesterol if it is raised and if they are at risk of developing cardiovascular disease.

Blood lipid (fat) levels, including cholesterol, are known to be associated with cardiovascular diseases, such as coronary heart disease and strokes.

While cholesterol levels are influenced to a large extent by environmental factors such as diet, genetics are also thought to affect them. People with a close relative with a history of high cholesterol have an increased risk of developing the condition themselves.

Special case control studies called genome-wide association studies (GWASs) are used to identify genetic variations that are associated with traits such as blood lipid levels.

The variations that are identified in these studies may themselves be directly influencing blood lipid levels, or may lie near to other variations that are having the effect.

A large meta-analysis combining the results of GWASs has previously shown that common genetic variations in at least 95 different places on our DNA are associated with blood lipid levels. To further identify other genetic variations that may have an influence on blood lipid levels, the current researchers combined the results of 32 GWASs involving 66,240 individuals of European ancestry.

Pooling the results of studies in this way means that the analysis includes larger numbers of people. This means it has more “power” to detect variants that may each be associated with only a relatively small effect on lipid levels.

The researchers analysed individual information for 22,471 Europeans in seven cohort studies, and an extra 25 cohorts provided summary-level results for an additional 43,769 people, to give a total sample size of 66,240. In addition to genetic data, where available, further information was obtained on BMI, age, gender, diabetes and smoking. Blood samples were collected for measurement of lipid levels in the individual studies, and they also looked at whether the people were taking cholesterol-lowering medications.

The researchers assessed a total of 49,227 single letter variations in the participants’ DNA. These variations lay in about 2,000 regions of the DNA that are known to contain genes that are mainly related to cardiovascular, inflammatory and metabolic traits.

The researchers looked at which of these variations were significantly associated with blood lipid levels. Essentially, they looked at whether people with a particular genetic variation had significantly higher or lower blood lipid levels than people without the variation.

The researchers found hundreds of variants significantly associated with each of the traits assessed – HDL (‘good’) cholesterol, LDL (‘bad’) cholesterol, total cholesterol or triglycerides.

The researchers then filtered their results to include only those variants assessed in 80% or more of the studies, and where the results showed a high level of consistency across studies.

After this additional filtering, they found significant associations with 549 significant single letter variations (SNPs) in the DNA that occurred in and around 114 different genes.

When they used models that took into account age, use of cholesterol medications, smoking, BMI and diabetes, they found similar results.

Overall, in genes previously demonstrated to be associated with blood lipids, they identified SNPs that had not been previously associated with blood lipids:

They also identified lipid-related SNPs in genes that had not previously been reported to be associated with blood lipids:

For the studies where they had individual participant data available, after adjusting for age and gender they estimated that the identified SNPs explained:

The researchers conclude that their large meta-analysis, combining the data from 32 studies identified many genetic variations that had not been previously established as being associated with blood lipids. They also similarly identified several genes that were not previously identified to be associated with blood lipid profile.

This large study has combined the results of 32 studies that have looked at the blood lipid profile and genetics of European populations. The researchers identified several new variations in genes already established to be associated with blood lipid profile, and several in genes not previously associated with blood lipid profile.

Overall, this study furthers our understanding of how genetics may influence the fats we have in our blood. Even so, these genetic variations will not provide the whole answer to blood cholesterol levels. The findings also may not apply to non-European populations. It is too early to know whether this study brings us “a step closer to preventing heart attacks” or paves the way for new treatments.

We do not currently have the ability to alter our genetics. What we can do to reduce our risk of cardiovascular diseases is to eat a healthy balanced diet high in fruit and vegetables, take regular exercise, stop smoking and drink alcohol in moderation.

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